I've recently recorded two programs from Showtime, an episode of Dexter and the movie World Trade Center. On both, the main audio voice track is missing. I still get background sound, theme music, etc. - but not the main voices. Don't have this problem with any other recordings or when watching Showtime live. This is on Comcast cable.

Is this some sort of copy protection from Showtime, a problem with my TIVO HD, or maybe a setting on my Receiver?

I have a sub-woofer, but not a center speaker - however, I didn't set the speaker connections up - so I'll have to check how its hooked up and set. Would I have this problem only with Showtime recordings? Thanks for the direction to look.